variable width bars in bar chart

I would like to plot a graph that looks like a bar chart, but I want to be able to specify the widths of the bars. For instance, if the user enters 0 for the x-min, 6 for the x-max then 5,000 for y-max I want to draw a bar that starts at 0, has a width of 6 and a height of 5,000. It seems the bar chart options on an xy graph don't allow for variable width, but instead center around whatever x value is associated with a particular y value.

Can I do this without actually having to manually plot each rectangle's vertical and horizontal line?